[Elecraft] KPA Fan Noise

[Wes Stewart]

I think there is fan noise then there is other fan noise.

I've built HP tube amps that required lots of air flow to live. See 
http://sadxa.org/n7ws.html for examples.  My thinking was that you could never 
have too much air.  That said, the blower noise was different in these from what 
my KPA500 emits.  In the 8877 amp for instance the blower IIRC, was rated at 
about 300 cfm.  But it operated into considerable back pressure from the inlet 
RF screen, the tube anode fins and the output grill.  Some of the noise was 
actually from the motor, not airflow.  Furthermore the amp was mounted in a 4' 
rack cabinet which further dampened noise.  It ran continuously and just became 
part of the background noise typical of a high power station and I lived with it.

I don't have a KPA1500, just a KPA500 but I can say that at fan speed 5 or 6 it 
is way obnoxious.  In fact, just before writing this I went into the shack in 
the next room from the office and cycled the speeds.  My lady who is sitting in 
front of her computer here in the office asked, "What is all that noise?"

I use a Yamaha CM500 headset at all times and I can say that a few nights ago 
when I operated as K7UGA and ran 300 Qs in 2 hours on 20 SSB the fan was pretty 
loud at times.

Wes  N7WS


On 6/2/2018 12:30 PM, William Levy wrote:
> I have been cooling amplifiers 1980. I built an 8877 amd it had a blower.
> I don't understand the fan noise problem. Tubes and Transistors need
> cooling.
> The more the better. Earphones are the answer if you can't hear the weak
> ones.
> Frankly I don't care about the weak ones. Probabliy can't hear the weak
> ones anyway at 70! I remember the very first Alpha has water cooling. That
> was a nuisance!
> 73 all,
>
> Bill N2WL
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